Next Up walked every series in an unpaginated loop and read user data one
episode at a time, so the Home screen row cost two queries per series once the
cache was gone.
- read the played state of every candidate episode in one query
- read the versions the resume check and the last played date need in one query each
- default PrefetchedUserData on IUserBaseItemComparer so plugin comparers still compile
- cover the bounded query count and the plugin comparer with tests
- share one database across the replica tests
